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LM5117-Q1: LM5117

Sambit Kumar P
Prodigy 40 points
Part Number: LM5117-Q1
Other Parts Discussed in Thread: LM5117

Tool/software:

Hello I am using LM5117 with switching freq 480KHZin my ECU during Radiated emission in 966KHZ and 160MHZ. When I checked with near field probe I am getting the emissions source is switching node . My voltage input is 28 V and output is 12V , 3A.I tried to reduce switching speed by increasing high side mosfet gate resistor value to 5-10 ohm range but no improvement was observed via near field probe. 3A.Can you please recommend here the snubber in switching node...in case any calculation sheet or any other way to reduce emissions. 

  • 0
    TI__Guru 59331 points

    Hello Sambit

    Please try these items. 

    • Make SW node copper area smaller. 
    • Add RC snubber between the drain and the source of the low-side MOSFET.https://www.ti.com/document-viewer/lit/html/SSZTBC7 
    • Populate a schottky diode in parallel with low-side MOSFET
    • Use shielded inductor with minimized pin lead exposure. The pin leads are hidden on the bottom side in this example. 
    • Locate the 'dot'  (or 'bar') direction of the inductor at the SW node. 

    -EL